The identiPol OIT

UK designed & manufactured

What is it?

The lifetime of a plastic component is mainly governed by its ability to withstand oxidation and
degradation. When exposed to the oxygen in the air that we breathe, plastics age and degrade over time,
losing mechanical strength and leading eventually to component failure.

The lifetime of a plastic can be increased by appropriate polymer chemistry or by adding additives (antioxidants)
to the plastic during processing. Generally, the lifetime is greater for materials having a higher
molecular weight, although performance of lower specification plastics can be enhanced with anti-oxidants.
However, as these additives are more expensive than the plastic granules, a balance is sought between
cost and performance. The OIT test is frequently used as an indication of sufficient molecular weight,
but in such cases it must be clear whether materials are tested with or without anti-oxidants.

The identiPol OIT is designed to provide unskilled staff with a simple tool to measure the oxidative stability
of a plastic using the internationally recognised Oxidative Induction Time/Oxidative Induction Temperature
(OIT) method.
The system has been specifically designed to conform to approved standards (ASTM D3350, D3895-07, DIN EN 728, ISO 11357-6) and be operated
alongside the production line by semi-skilled staff.

What does it do?

There are two modes of operation for the
identiPol OIT:

Oxidative Induction Time

In this mode a sample of plastic is heated in
an inert atmosphere (typically nitrogen), to a
given temperature appropriate for the type of
plastic. (For example, PE would be heated to
210°C). The temperature is held constant and
when the temperature reaches a stable value,
the gas is switched automatically from nitrogen
to air. The time elapsed from the switch in gases
to the moment the plastic starts to oxidise and
decompose defines the Oxidative Induction Time.

Oxidative Induction Temperature

In this mode a sample of plastic is heated in an
atmosphere of air, at a constant heating rate, until
the plastic starts to oxidise and decompose. The
onset of this decomposition reaction defines the
Oxidative Induction Temperature.

How does it work?

When a plastic material undergoes oxidative
degradation, heat is evolved. By measuring the
temperature of the plastic and comparing it to
the temperature of its nearby surroundings, a
temperature difference can be measured when
the plastic starts to oxidise.

Test samples are first moulded within the identiPol
OIT to produce a consistent sample for
measurement. The test sample is then heated up
while the temperature difference of the sample is
compared to an inert reference temperature. The
temperature difference is then measured as the
plastic is heated or held at a constant temperature.

Either the heating stops at a given temperature to
measure Oxidative Induction Time, or continues
to measure the Oxidative Induction Temperature.
A rapid increase in the temperature difference
between the plastic sample and the reference
is used to indicate the onset of oxidation
and decomposition.

At the end of the measurement the plastic
sample is discarded and the built-in
software calculates and stores all relevant
information. A certificate of OIT
conformance can be printed and used as
part of your, or your customer's, quality
control process.